1. Field of the Invention
This invention relates to a photographic camera and a method of and a device for distinguishing the condition of use of a film in a film magazine.
2. Description of the Prior Art
There has been known a film magazine in which a data disk carrying thereon bar codes representing information inherent to the film magazine such as the ISO sensitivity, the number of exposure frames and the like of the film is provided to rotate integrally with the spool. The bar codes comprise a plurality of bars of a low reflectivity and spaces of a high reflectivity which are alternately arranged in the direction of rotation of the data disk. Further a particular portion such as a black quiet zone showing a data read begin position or a data read end position is provided at the leading end and/or the trailing end of the bar codes.
Further there has been known a photographic camera in which a film magazine provided with such a data disk is loaded as disclosed, for instance, in U.S. Pat. No. 5,025,274. The camera disclosed in the United States patent is provided with a photosensor for reading the bar codes, and the bar codes are read by the photosensor while the film is initially set. The camera automatically adjusts various mechanisms in the camera such as the stop on the basis of the data read by the photosensor.
In such a film magazine, no part of the film projects outside the magazine body except when the film is exposed to take a picture, and accordingly whether or not the film has been exposed cannot be known from the appearance of the film magazine. Thus there has been proposed a film magazine which is provided with an indicator which indicates the condition of use of the film in the magazine, that is, whether the film is virgin, the film has been partly exposed or the film has been fully exposed. See, for instance, U.S. Pat. Nos. 5,049,912; 5,049,913 and 5,047,794.
As the indicator, there have been disclosed, for instance, in Japanese Unexamined Patent Publication No. 5(1993)-313234, one which points one of a plurality of marks provided on the magazine body, the marks representing different conditions of use, and one in which a part of the data disk doubles as the indicator. When the film magazine provided with such an indicator is taken out from the camera, the film is fully retracted in the magazine body irrespective of the condition of use of the film and the spool is positioned in a predetermined angular position according to the condition of use of the film, which causes the indicator to point the mark corresponding to the condition of use. Accordingly the condition of use of the film can be known from the position of the indicator.
However, some user can overlook the indicator and load a fully exposed film magazine in the camera without knowing that the film has been fully exposed. In such a case, the camera naturally does not operate but the user can mistake it for a failure of the camera.
Further there also has been known a camera in which a film magazine having a data disk provided with a cutaway portion indicating the condition of use of the film is loaded and in which a mechanical sensor is provided to be brought into abutment against the cutaway portion when the film magazine is loaded. When the data disk is rotated in response to rewind of the film and the sensor detects the cutaway portion, the spool drive shaft is stopped. However this camera is disadvantageous in that a larger space is required in a camera body to accommodate the mechanical sensor in addition to the photosensor for reading the bar codes and the manufacturing cost increases due to increase in the number of parts. Further information on the condition of use of the film can be expressed only by the presence or absence of the cutaway portion and only two conditions of use can be expressed.
Thus there has been a demand for a method and a device which can distinguish three or more conditions of use of the film with a simple structure in a short time.
In a motor-driven camera, the film is generally rewound into the magazine after all the frames are exposed. The driving motor is kept driven for a predetermined time after the film counter comes to show 0 so that the film is completely rewound into the magazine.
Recently there has been proposed a film magazine of novel type having a light-shielding door which opens and closes a film exit slit. See, for instance, U.S. Pat. Nos. 5,049,912; 5,049,913 and 5,047,794. The film magazine of this type is provided with a spool which is rotatably supported in a magazine body and around which a film is wound and when the light-shielding door is opened, the spool is permitted to rotate relative to the magazine body to feed the film in and out the magazine body. When the door is closed, the film is wound into the magazine body and at the same time the inner space of the magazine body is closed in a light-tight fashion. Further the film magazine is provided with a data disk carrying thereon information inherent to the film magazine such as the ISO sensitivity, the number of exposure frames and the like of the film to be rotated together with the spool.
Also in the case of a photographic camera using the film magazine of this type, the driving motor must be kept driven for a predetermined time after the film counter comes to show 0 so that the film is completely rewound into the magazine as in a photographic camera using a conventional 135 film (35 mm film).
The predetermined time by which the motor is kept driven after the film counter comes to show 0 is generally set sufficiently longer than the time which is normally required for the film to be completely rewound into the magazine body taking into account a reduction in a motor speed and the like due to, for instance, a low ambient temperature. Accordingly, in the normal environment, the rewinding operation can be continued in vain even after the film is completely rewound into the magazine body, which causes the user to feel the rewinding time to be too long.
Especially when a whole roll of film is consumed in the course of photographing, it is preferred that the film magazines be changed as quickly as possible and accordingly film rewinding is required to be carried out in a shortest possible time.
Further from the viewpoint of saving power, it is not preferred that the motor is kept driven in vain.